Thirty-three percent of Americans don't believed in evolution, according to a Pew survey released today. Above, the 500,000-year-old skull of Homo heidelbergensis. (Photo: Reuters)

Thirty-three percent of Americans agree with the statement "humans and other living things have existed in their present form since the beginning of time," according to a Pew Research survey released today. In a national phone survey of about 2,000 adults, 60 percent of Americans agreed that "humans and other living things have evolved over time." That's roughly the same share of Americans who believe in evolution since that last time Pew conducted such a poll, in 2009.

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What has changed greatly since 2009 is the American public's belief in evolution when viewed along party lines. Forty-three percent of Republicans say they believe humans and other creatures have evolved, down from 54 percent of Republicans who believed that in the 2009 survey. Forty-eight percent of Republicans say that humans have not evolved since the beginning of time.

There was also a shift in the number of Democrats who believe in evolution, but unlike Republicans, that figure moved up. In the 2009 Pew survey, 64 percent of Democrats professed a belief in evolution, a number that increased to 67 percent this year.

Taken together, that means the gap between the number of Democrats and Republicans who believe in evolution has grown from ten points in 2009 to 24 points in 2013. "It's an intriguing finding that is suggestive of greater polarization," said Cary Funk, a senior researcher at the Pew Research Center's Religion & Public Life Project and Social & Demographic Trends project.

Party affiliations aside, half of Americans who say they believe in evolution express the view that evolution is "due to natural processes such as natural selection." About a quarter of American adults agree that "a supreme being guided the evolution of living things for the purpose of creating humans and other life in the form it exists today."

Among those who express a belief in evolution, 24 percent say that "a supreme being guided the evolution of living things for the purpose of creating humans and other life in the form it exists today." Thirty-two percent say that evolution is "due to natural processes such as natural selection."

Americans are generally less accepting of evolution than other Western nations. In a 2006 study published in the journal Science, researchers compared surveys conducted in 32 countries since 1985. They found that only 14 percent of U.S. adults believed that evolution was "definitely true," with roughly a third saying it was false. Of the 32 nations in the study, the U.S. expressed the second-smallest belief in evolution, with only Turkey below it.

The nation that was found to believe most in evolution in the 2006 study was Iceland, with about 80 percent believing evolution to be fact. It's an interesting nation that both overwhelmingly believes in evolution yet also believes in elves enough to halt construction of a highway because it would allegedly run over elves' land.